1. Field of the Invention
This invention pertains to the field of pipe joining or coupling, and more particularly to pipe joints which allow greater joint deflection than prior art push-on pipe joints.
The invention relates to connecting pipes using push-on joints wherein an elastomeric seal surrounds the end of one pipe and seals against the inside of the other pipe being joined. Such joining methods are designed to allow a certain deviation from a straight line when any two pipes are joined. Also, when a fitting is joined to a pipe, there can be a deviation from the precise angle intended for the fitting. Such deviation can be multiplied utilizing the present invention.
The invention comprises a pair of pipes coupled together using a "nested" coupling. The end of one pipe is inserted into sealing engagement with an internal coupler, i.e., a bell stub (having a bell contour inside and a plain end contour outside) which is itself inserted into sealing engagement with the bell of a connector or the bell of a pipe. Two plain end pipes can thus be joined in such a manner as to allow four times the joint deflection as a bell and plain end joint would have. Additional "nests" could be utilized to further increase the deflection, or a bell to plain end connection can be made utilizing one bell stub piece to double the normal deflection. Restraining means can also be incorporated into the connection.
Prior art push-on joints can be deflected until the end of the plain end pipe being joined comes into contact with the inside surface of the bell of the outer pipe being joined. Such joints will not deflect further without permanently deforming their shape. A restrained pipe joint of the prior invention is disclosed and claimed in U.S. Pat. No. 3,684,320.
The nested joint of this invention will allow the inner joints to deflect to a maximum and allow the outer joints to deflect likewise. Thus, multiple joint deflections are allowed in an equal length of the pipe line. This is especially useful when traversing uneven terrain where excavating is not possible or cannot be controlled, e.g., when crossing a stream or descending a mountain. It is equally important in an area where considerable soil movement or settling is anticipated such as swamp lands or earthquake-prone areas. Prior art methods are limited to the use of short lengths of pipe or to joints utilizing a ball and socket. Ball and socket joints require expensive machining to close tolerances. The present invention can utilize molded components which are not machined. This is a significant savings especially for ductile iron pipe lines as will be seen in the description of the preferred embodiment of the invention.